Given the pernicious reach of obesity and the evidence that current behavioral treatments are modestly effective at changing weight, efforts to refine behavioral recommendations in order to improve weight loss interventions are crucial. Frequency of tracking body weight presents itself as a prime target for behavioral enhancement during weight loss. Daily self-monitoring (e.g., of dietary intake and physical activity) is alread well-established as a central component of the behavioral weight loss process. However, the current standard of care in behavioral weight loss with regard to weighing is weekly tracking of weight, and some programs caution against any weight tracking. It has been suggested that frequent weight tracking may have a negative impact on mental health and outcomes during weight loss, but there are minimal data that address this concern experimentally in the context of an active weight loss program. Observational evidence from behavioral weight control trials and community studies suggests that greater frequency of tracking weight is associated with better weight outcomes. Stronger experimental evidence is needed to establish a causal link between weight tracking and weight outcomes and to elucidate the impact on mental health during weight loss. To achieve the long-term goal of strengthening behavioral weight loss programs, the purpose of this project is to test an enhanced, daily weight tracking instruction against the current standard of care (weekly weight tracking) and an alternate model of care with very limited data (no weight tracking). In pursuit of study goals, 336 overweight and obese adults will be recruited and randomized to one of three 12-month weight loss interventions with a 12-month follow-up (24 month study endpoint): the standard of care (weekly weight tracking during weight loss), an enhanced condition (daily weight tracking during weight loss), or a comparison condition (no weight tracking during weight loss). The rationale behind this proposal is that within the context of social ecology and a social-cognitive framework of behavior change, enhancement of this key environmental feature (i.e., the weight tracking environment) during weight loss will contribute to success by promoting self-efficacy for this critical behavior. Speciic aims of the study will seek to determine the effects of weight tracking frequency on the weight loss process and outcomes, as well as to elucidate the effects of weight tracking frequency on mental health during weight loss. This study will have the expected outcome of enhancing the standard of care for weight loss, leading to better weight control for overweight and obese adults and thus directly mitigating the public health impact of the obesity crisis.